Saddam ran a terrorist regime that home to a devil's brew of terrorist groups ranging from socialist to Islamist. They were a tool of Iraqi policy against the democratic West and Iraq's neighbors. Then too, Al Qaeda had a haven in Iraq under Saddam's supervision. It emerged in full virulence at the end of the war because the downfall of Saddam's regime eliminated the totalitarian constraints that kept it in check. This is not to say the Ba'ath regime was a civilized government before we came in that wanted peace with the rest of the world. All the evidence to date has demonstrated that was definitely not the case.
(Denny Crane: "Sometimes you can only look for answers from God and failing that... and Fox News".)